The studies of this project are those of the ongoing development and applications of an in vivo, in situ animal model system using juvenile sheep for evaluating cardiac valves and cardiovascular flow dynamics. Previous years' studies have concentrated upon conventional hydraulic and hemodynamic evaluations of normal cardiac valves and prosthetic cardiac valvular substitutes, and upon morphologic and physical characterization of calcific degeneration of bioprosthetic valves. Current efforts emphasize studies of intracardiac flow dynamics for quantifying the pathophysiologic abnormalities occuring with stenotic and regurgitant lesions of both native and prosthetic cardiac valves. During the past year two types of experimental preparations of mitral regurgitation and two types of experimental preparations of mitral stenosis have been investigated using color Doppler flow mapping technology. Animals with mitral regurgitation due to perforated leaflets or due to disrupted chordae tendineae were studied to determine regurgitant flow volume and regurgitant fraction. Animals with mitral stenosis due to mitral annular constriction or due to calcified bioprosthetic valves were studied to determining stenotic orifice area and transmitral flow. These studies demonstrate: 1) that observations of convergent flow using principles of momentum continuity preservation may be used to evaluate intracardiac hemodynamic pathophysiology; and 2) that clarification of both spatial (geometric) and temporal (pulsatile) characteristics are important in applying fundamental physical theories of fluid mechanics to the complexities of cardiac valvular flow dynamics. The studies explore methodology, illustrate principles, and demonstrate the validity and utility of these non invasive techniques for obtaining clinically relevant quantitative information.